Enhanced Thermal Performance of Fiber-Reinforced Cementitious Composite with High-Volume Fly Ash and Steel Slag Aggregates

Existing cementitious composites often undergo severe degradation when exposed to high temperatures. The present study proposes utilization of high-volume fly ash (HVFA) and steel slag (SS) aggregates to address this issue. Hybrid fiber reinforcement in the form of basalt fibers and polypropylene (PP) fibers have also been utilized. A total of 120-cylinder specimens were cast for the elevated temperature testing between 200°C and 800°C, and the residual compressive and microstructural properties were analyzed. Results indicate that the HVFA mixes with 100% SS fine aggregates and hybrid length basalt fiber yield optimal performance at elevated temperatures. Specifically, the mix containing 100% SS aggregates retained 101%, 115%, 113%, and 55% of its compressive strength at 200°C, 400°C, 600°C, and 800°C, respectively. Microstructural analysis further revealed that the use of HVFA-SS system enhanced the elevated temperature performance by promoting the pozzolanic reaction of slow reacting fly ash particles, tobermorite formation, and improvement in the interfacial transition zone. Also, excellent resistance to cracking and spalling was observed. Overall, this study provides new perspective on the design of sustainable fiber-reinforced cementitious composites with excellent thermal endurance.